1. Field of the Invention
The present invention is generally related to a bow string release and is specifically directed to a release head.
2. Description of the Prior Art
Mechanical archery bow string releases have become increasingly popular in recent years because they provide uniform control of the bow string and increase accuracy by effecting the consistent, controlled release of the arrow. Bow string releases are typically used to maintain the bow string in a cocked position in which the bow string is flexed against the tension of the bow for propelling the arrow supported on the bow string. When a drawn arrow is released from a release mechanism, the release is usually relatively rapid and at a point approximately in line with the centerline of the bow so that the bow string delivers most of its thrust directly along the major axis of the arrow. When tabs or fingers are used to release a bow string, the bow string tends to roll off the fingers or tab and be deflected sideways during release such that the bow string follows a serpentine path, failing to maximize energy delivery directly along the major axis of the arrow.
The arrow itself is generally comprised of a shaft with a point mounted on one end and a nock mounted on the opposite end. A standard arrow nock has a bow string receiving groove or notch defined by spaced apart legs extending from a base. The nock is configured to receive a bow string and insure stability of the arrow when the bowstring is drawn and released. When an arrow is loaded on a bow in this manner, the legs of the arrow nock extend beyond the bow string toward the archer such that and arrow can rotate about the bow string. When engaging the bow string, the nock is preferably seated at or near the mid-pint of the bow string to insure that the flight of the arrow is as true as possible.
The majority of the bow string releases have a body or casing which houses the sear and trigger mechanisms. The body is typically a cylindrical or rectangular design with the pivotable jaws of the sear mechanism positioned at one end and a trigger located along the length of the body. The release employs a trigger mechanism to activate the bow string retaining and release mechanism. The jaws and trigger mechanism of the bow string release are traditionally secured to the body with linkages or pins, which serve as a pivot mechanism for the jaws and trigger.
Recently, receivers for bow string releases have become increasingly popular. One example of such a receiver is disclosed in U.S. Pat. No. 5,850,827, assigned to Tru-Fire Corporation. When using a receiver, the archer attaches the bow string release directly to the receiver, instead of to the bow string. Instead of releasing the bow string, the release grasps and releases the receiver, which in turn allows the string to advance and propel the arrow forward.
Rope loops are also used in this capacity as a receiver. A short piece of rope, ordinarily approximately 2 mm in diameter, is attached to the bow string both above and below where the arrow nock rests. The perceived advantages of using a rope loop are varied. Once an archer employs a rope loop, the archer may find that it is difficult to engage the bow string release with the rope loop, due in part to the very resilient nature of rope.
Because of the difficulty in attaching bow string releases to rope loops, different bow string releases adapted to more easily grasp rope were introduced, including that disclosed in U.S. Pat. No. 5,680,851 to Summers, which is incorporated herein by reference. Other bow string releases adapted to more easily grasp rope include the Tru-Fire Corporation""s xe2x80x9cTru-Caliperxe2x80x9d line of releases.
Draw weight of a bow is ordinarily measured in pounds, and is the force required to pull back a bow string from a static position to a full draw position. Effective draw weight of the bow is the draw weight after let-off is factored. Effective draw weight is the force required to hold the bow string at full draw in the firing position. Common bows have draw weights of up to 100 pounds, and let-offs of up to 80%, decreasing the draw weight that the archer feels at full draw by the let off percentage.
It has been found that many commercial bow string releases, including a release referred to as a Tru-Ball xe2x80x9cTornadoxe2x80x9d release, xe2x80x9cload upxe2x80x9d severely as pulling force on the bow string is increased. xe2x80x9cLoading upxe2x80x9d is a phenomenon whereby the force required of the archer to pull the trigger and release the bow string increases as the effective draw weight of the bow increases. Thus, at higher effective draw weights, the archer must pull harder on the trigger, perhaps causing a decrease in sensitivity and performance. A harder trigger pull may also cause a jerking trigger release motion, causing erratic arrow flight.
There are two common trigger sensitivity adjustment mechanisms used widely. In one mechanism, the depth of engagement of sear elements is varied. This affects trigger pull length, also known as trigger travel distance, and indirectly affects pull force required by making the trigger travel farther to disengage the sear, which in turn increases the sliding friction. An example of this mechanism is U.S. Pat. No. 5,680,851 to Summers.
Another mechanism is a single roller on one sear element, sear element, typically mounted on one jaw, positioned in an angled slot in the other sear element, typically a slot in the trigger. Examples include a release known as the Scott Caliper release. In this mechanism, a roller is used to reduce friction between the sear elements. Adjustment is related to the positioning of a roller""s center in relation to the edge of the angled slot. This limits the upper end range of trigger force required due to the rolling force in the slot. At the lower end of the pull force range, the roller center is balanced on or just outside the slot edge. If the roller center is outside the slot edge, the release will not stay closed during bow draw unless a force is applied to overcome the center over the edge condition created.
The only known release that changes the angle of contact between sear members and therefore permits incremental linear adjustments of trigger force is Tru-Fire""s Classic Caliper as described in U.S. Pat. No. 5,582,158.
The present invention provides a bow string release mechanism that is easily attached to a bow string or a receiver. An archer""s index finger pulls the bow string release of the present invention to open jaws on the release, and relaxes tension on the trigger to close the jaws. The jaws can be closed around a bow string, a receiver or the like. This convenient system allows the archer to maintain one finger on the trigger of the release to load the release onto the bowstring or receiver, and to relax the trigger to finalize loading by closing the jaws of the release.
The same trigger is used to release the bow string from full draw to propel the string and the arrow.
In one embodiment, the trigger is separated from the jaw to allow for smoother operation at all trigger sensitivity settings, particularly at fastest or lightest settings. In this embodiment, the trigger is not an integral sear element, and transmission of forces and slight movements are transferred to a roller axle linkage assembly from the jaws. This allows for reliable lower trigger settings.
It has been found that bow string releases according to the present invention advantageously minimize xe2x80x9cloading up,xe2x80x9d thereby minimizing the force required of the archer to pull the trigger and release the bow string as the effective draw weight of the bow increases.